It does fit on our king size bed. For it being the 'tall' version, it could be a little bit taller, but we do have a thick mattress. Sturdy and easy to assemble

I have a queen size bed with slats under a pillow top mattress. This works perfectly with those high hinges!
Negatives:
1) The instruction is over-simplified
A) You need to put the cover on one side BEFORE snapping them together. The instruction sheet shows it, but doesn't say it.
B) It was difficult to figure out how to use the pull-up release levers to lower the rail. The instruction sheet doesn't clearly identify them nor explain how they work.
2) The release mechanism is very tight. Possibly due to the snug fit of the cover. It's VERY difficult to budge the locks when my arthritis acts up. Someday I'll remove the cover to see if that makes dropping the rail less difficult.

However, the negatives aren't a deal-breaker for me. This product does what I need it to do, at a price that's reasonable. I'd buy it again.

I didn't think these would be nearly as great as they are. I LOVE THEM. I have one on each side of my sons bed (very active sleeper). The are extremely durable and tough. They are not plastic, but steel. A pain to install, but worth the time and effort and not really that hard at all. They also make changing the sheets and covers hard, but again its a small price to pay for his safety. His bed sits 3 feet off the floor and he kept falling out of the bed. It was a miracle that he didn't hurt himself. I've slept in his bed several times and they hold up beautifully with me pushing against them. I would buy again and I definitely recommend.

We've only had it for about two weeks, but so far my 2yo has not fallen out of his new bed. In fact, the first morning I came in to find him asleep between the mattress and the rail, like he would had fallen had the rail not been there and the rail held him so "snug" and comfy that he just kept sleeping. He kicks it, leans on it, and it's now showing any signs of coming out. I haven't given it five stars because I thought the security belt that goes to the other side of the mattress was very difficult to tighten. I also see a warning label that says not to use it on a bunk bed - I wonder if that is referring to the top bunk as we are about to get bunks and the 2yo will be on the bottom, I'd like to be able to use it there and I'm not sure why I couldn't.

We had to move our daughter to a "Big Girl" bed sooner than we would have like because of us expecting our 2nd child. We got a daybed that is covered on three sides with wood. So I ended up buying two of these and it goes the whole length of the bed, so its pretty much makes the bed a bigger crib. But since I made it into a crib like bed, it is really nice that the sides fold down and allows her to get into bed and allows us to read to her while she is in bed. And in the mornings when we get her up, it allows her to get down by herself. I think it makes he feel more like a big girl. At times though it can be a little difficult to lower the rail. But I don't really see that as a bad thing since I feel like it keeps her in there more securely!